Back when he was hailed near and far as one of the NFL’s sharpest talent men, back when the Chargers were coming off their fourth consecutive playoff trip, A.J. Smith fell in love with a running back named Ryan Mathews and wagered a gigantic draft-day bet on the Fresno State junior.

The Chargers haven’t returned since to the playoffs, and although the reasons for it go far beyond Mathews, in the end, Smith and Norv Turner lost not only all their poker chips, but their patience with No. 24.

Now it’s Mike McCoy who must figure out the 26-year-old who's a potential coach killer because he’s also a potential star.

In three exhibition games, Mathews has shown McCoy reason to believe he can ignite San Diego’s ground game and in turn the play-action attack.

Then again, his career ledger offers nearly as many career fumbles (12) as touchdowns (14).

Saturday against the Cardinals, McCoy saw that scary guy up close for the first time.

The Chargers were inside Arizona’s 1 late in the first half when Mathews took a handoff from Philip Rivers and ran straight ahead.

When Mathews started to launch himself – reprising a tactic that converted a fourth down against the Seahawks and brought him six points against Arizona – a defender from his left slid off King Dunlap’s block and rammed the ball with his helmet.

The ball went flying. The slapstick that followed – the Cardinals' failed lateral that resulted in a Chargers TD – didn’t change the fact: a fumble on first-and-goal from 20 inches out.

McCoy praised Cardinals end Calais Campbell for “coming from a good angle,” and dislodging the ball.

He added: “Any turnover you have, you’re going to try to correct it.”

I asked McCoy if he still trusted Mathews near the end zone, post-fumble. “We were going to give it to him again the next play,” he said.

Once a fumbler, always a fumbler? Maybe. Mathews lacks large hands and is a tad upright, exposing him to more direct hits, and I doubt he lacks for instruction. Running backs coach Ollie Wilson tutored LaDainian Tomlinson, who went from being a fumbler to a touchdown machine.

But giving Mathews another crack at the TD would've been smart. Play the confidence game.

The new bosses seem to be pulling out all the stops to both toughen and embolden him. Tom Telesco supplied a forceful run blocker in D.J. Fluker. McCoy and Ken Whisenhunt insisted he run north-south. Once he pounded out those kind of yards -- against starters for the Seahawks and Bears -- the coaches sprang him with draw plays against the Cardinals. Earning trust, Mathews bounced east-west for a rewarding gain.

But the fumble was jarring and spooky because it recalled his fumble against the Falcons in Week Three last season, also near the end zone, also after he'd run past and over defenders in several carries. Instead of taking the lead against Atlanta, which was the better team, the Chargers lost in a rout. Both Smith and Turner seemed to blame Mathews for, if not all of the defeat, a large chunk of it. Without mentioning him, Smith jabbed him in the U-T a few days later. Turner yanked him from the starting lineup. Norv never again seemed to fully trust him near the end zone.

Mathews, remember, was playing for the first time since fracturing a collarbone six weeks earlier. By the time he cracked his other collarbone in December, Dean Spanos had all but decided to fire Smith and Turner.

McCoy and Telesco will survive, regardless of what Mathews does this season. They're less invested in him than Smith and Turner were. Taking to the press, Mathews seems more at ease. He said it's been a fun several months.